The GLI 18’ x 40’ Rectangle In-Ground Pool Estate Winter Pool Cover is a 23’ x 45’ winter pool cover made of tough polyethylene fabric. It is one of the toughest, most durable materials available. This material won’t crack, split, or tear from the cold winter elements. The lightweight cover is easy to put on and take off, and uses less room to store. The GLI Estate Plus pool cover edges have been double-folded and double-stitched with a water, chemical, and sun resistant thread, ensuring that the reinforced seams last longer, without fraying or coming apart. The 23’ x 45’ cover prevents algae growth and keeps the pool water clean and free from dirt, leaves and debris.